This application claims priority to an application entitled xe2x80x9cMobile Station Positioning Device And Method in Mobile Communication Systemxe2x80x9d filed in the Korean Industrial Property Office on Sep. 16, 1998 and assigned Serial No. 98-38278, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates generally to a mobile communication system, and more particularly, to a mobile station positioning device and method in a mobile communication system.
2. Description of the Related Art
The FCC (Federal Communications Commission) demands that a service for positioning all mobile stations (MS) at probability of 67% within a permitted error limit of 125 meters should be implemented by October 2001 for emergency 911, E911. Designers are attempting to implement this service using a reverse link FICTION called PUF (Power Up Function) in the IS-95 CDMA (Code Division Multiple Access) standard supplied by TIA/EIA, as well as in the IMT(International Mobile Telecommunication)-2000 system.
The PUF is a function for measuring the distance between a mobile station and each of a plurality of neighboring base stations. The PUF uses the phenomenon that in case of emergency, the mobile station increases transmission power to the plurality of neighboring base stations. Each of the plurality of neighboring base stations then estimates the time required to receive signals from the mobile station. Accordingly, each of the plurality of neighboring base stations can then calculate their distance to the mobile station. However, the PUF is defined in the IS-95B standard, and therefore, the PUF causes an increase in interference. Thus, system efficiency and performance decreases.
It is, therefore, an object of the present invention to provide a mobile station positioning device and method using arrival time differences or time difference of arrivals (TDOAs) calculated with signals received from a plurality of neighboring base stations to the mobile station in a synchronized CDMA mobile communication system.
To achieve the above object, there is provided a mobile station positioning method, wherein a mobile station receives signals synchronized and transferred from at least three neighboring base stations at a predetermined time, wherein the mobile station belongs to one serving base station out of the at least three neighboring base stations. The mobile station positioning method including the steps of performing a forward transmission power control at at least one of the three neighboring base stations; calculating, at the mobile station, arrival time differences between two of the signals received from the at least three neighboring base stations; transmitting, at the mobile station, the arrival time differences to the serving base station; and estimating, at the serving base station, a position of the mobile station using the arrival time differences.
A mobile station positioning system is also provided including at least three neighboring base stations for transmitting signals synchronized at a predetermined time and controlling forward transmission power of the signals during a scheduled time interval; a mobile station calculating arrival time differences between two of the signals received from the at least three neighboring base stations; and a serving base station included in the at least three neighboring base stations for receiving the arrival time differences from the mobile station and determining a position of the mobile station using the arrival time differences.